Figure 9. Yellowfin Tuna Catch/ 100 Hooks January- 

 June). Another group of four fishing sections in February, March, 

 May, and June suggests a wider spread of mediunn concentrations 

 and no really high concentrations oi yellowfin tuna. Otherwise the 

 pattern is very much the same. We do not consider the above or 

 the previous chart as being very accurate. Too many different 

 months are grouped together and there are not enough repeated 

 fishing trials for the same months. Until our survey plan is com- 

 pleted, these should only be regarded as tentatively describing the 

 distribution. Even so, it is beconning clear that certain areas along 

 the tuna-rich equatorial belt contain more tuna than others and 

 during some periods of the year the tuna are more concentrated. 



Translating these concentrations in to commercial fish- 

 ing yields, a vessel fishing on the grounds that average 6 tuna per 

 hundred hooks would catch 180 tons per month, if it fished the sanne 

 amount of gear (2, 000 hooks) as is normally operated by Japanese 

 longline vessels. But without lavish use of manpower, it is diffi- 

 cult to handle daily this much gear. The American vessel shown in 

 figure 17 set less than 500 hooks per day. 



10 



